Paper base planographic printing plates



United States Patent Ofi ice Patented Dec. 12, 1967 3,357,352 PAPER BASEPLANOGRAPHIC PRINTING PLATES Henry P. Williams, Jr., Combined Locks, andDonald A.

Rosenbohm and William H. Page, Appleton, Wis., assignors to AppletonCoated Paper Company, Appleton, Wis., a corporation of Wisconsin NoDrawing. Filed Aug. 12, 1965, Ser. No. 479,343 13 Claims. (Cl. l01462)This application is a continuation-in-part of our prior co-pendingapplication Ser. No. 339,888, filed Jan. 24, 1964, now abandoned.

This invention relates, generally, to innovations and improvements inpaper base, planographic printing plates or paper masters, and methodsof making the same.

Paper base planographic printing plates, and the methods of making andusing the same, are well known to those skilled in the art pertainingthereto, having been first commercially introduced over 20 years ago,Planographic printing is a form of lithography and therefore dependsupon the immiscibility of greasy lithographic printing inks and aqueousetch or lithographic solutions. In use, a paper lithographic orplanographic printing plate is first imaged in known manner with thetyped, Written, or drawn copy material to be reproduced so as to deposita grease-receptive imaging material which makes imaged areasinkreceptive and water-repellent (i.e. hydrophobic). The non-imagedareas are water-receptive and ink-repellent (i.e. hydrophillic). Theimaged plate is then placed on the plate cylinder of an offsetduplicating press. The over-all surface of the plate is then treatedwith an aqueous wet-out liquid, such as a solution of glycerin slightlyacidified with phosphoric acid, acid phosphate, ammonium nitrate, orother known substances. The aqueous wet-out liquid will wet all portionsof the plate surface except those that have been imaged and arewater-repellent. The press inking roll then passes over the surface ofthe plate and deposits a film of ink only upon the ink-receptive imagedareas. In the printing operation the ink from the imaged areas istransferred in reverse to the rubber offset blanket which in turn printsdirectly onto the paper sheet so as to form each copy.

A number of different coating formulations and techniques have beenutilized in the past to provide paper base sheets or webs with suitableplanographic printing surfaces. Normally, multiple coating layers ordepositions are used in the production of planographic printing platesor paper masters of the class described. For example, a so-called blackcoat may be applied to one side (back) of the paper web so as to impartdimensional stability to the plate and prevent curling. On the oppositeside (front) a seal or barrier coat is applied. Over the barrier coat onthe front side a face coat can be applied which becomes the printingsurface. Then, a wash coat is applied over the base coat for the purposeof insolubilizing the face coat. After each coating layer is applied ithas to be dried. It will be appreciated that each coating requires theweb to be run through a separate coating station and the machine timeand labor required comprise an important portion of the cost of thefinished plates or masters.

It has been found in accordance with the present invention that printingplates of good quality can be made in which the multiple coats or layersnormally applied to the printing or functional side of the paper web arereduced to a single coating layer or deposit. Similar proposals may havebeen made before but it is not known that any of these prior proposalshas gained commercial acceptance. In one embodiment of the presentinvention the functional or front coating formulation may also be usedas the back coating and the two coatings applied in a two-side coater sothat only one pass through the machine is required.

The object of the invention, generally stated, is the provision ofplanographic or lithographic paper base, printing plates or papermasters wherein the usual multiple coating layers, (cg. the seal orbarrier coat, the face coat and the wash coat) are consolidated into onefunctional coat or layer.

A further object of the invention is the provision of coatingformulations which contain all of the ingredients necessary to provide agood quality planographic or lithographic printing surface in a singlecoating application on one side of a paper base sheet or web.

Certain other objects of the invention will, in part, be

obvious and in part appear hereinafter.

For a more complete understanding of the nature and scope of theinvention reference may now be had to the following detailed descriptionthereof wherein a working example and certain permissible variationstherein are set forth whereby the invention may be practiced on acommercial scale.

Example I The paper base sheet or web may be any of the suitable knowntypes or grades of raw stock heretofore used for making planographicprinting plates.

Step ].-A paper web having a basis weight of approximately 50 poundsbased on a ream of 500 sheets cut to a size of 25 x 38 inches in firstcoated on one side with about 10 pounds dry weight per ream of afunctional coating composition having the following formulation, thecoating being dried in known manner so as to achieve a web temperatureof at least about 100 0.:

Lbs. Water 94.8 Polyvinyl alcohol (PVA powder) 6.2 Cypel Resin EmulsionNo. 205 3.1 50% Stellar Clay Slip (kaolin clay) 49.6 Melamineformaldehyde (Parez Resin No. 613) 2.3 Salt solution containing 7.5%aluminum chloride and 1.5% zinc acetate 43.0

In the above formulation the Cypel Resin Emulsion contains approximately43 to 45% solids which comprise a mixture of approximately 63% (byweight) ethyl acrylate, 35% acrylonitrile, and about 2% methacrylicacid. This preparation is currently available under the proprietary nameCypel Resin Emulsion No. 205 from American Cyanamid Company.

The foregoing coating composition may be formulated from the specifiedingredients in accordance with the following make-down procedure:

The PVA powder is first thoroughly dispersed in cool or cold water. Thetemperature of the dispersion is raised to C. and held between 90-95" C.for at least 30 minutes. To the resulting PVA solution, the Cypel ResinEmulsion, pigment slurry, Parez Resin solution, and salt solution areadded in the order named, with moderate agitation. A suitable defoamermay be added if needed, following adition of the Parez Resin solution.After each ingredient is added, preferably a short period of mixing isallowed before addition of the next ingredient.

After all the ingredients have been added and sufiicient mixing time forthorough blending has been allowed, the temperature of the blendedadmixture is raised to 90 C. after which the blend may be allowed tocool to room temperature on standing. Alternately, after being held at90 C. for 30 minutes the batch may be cooled rapidly as by the additionof ice.

Step 2.To the previously uncoated (i.e. back) nonprinting side of thepaper web their is next applied a back After the back coating has beenapplied, dried and calendered, the formation of the paper masters orprinting plates is complete except for slitting and cutting the rolledweb into individual plates of the desired size.

The proportions of the constitutents in the foregoing functional coatingformulation for the printing surface of the plate may be varied withinthe limits indicated in the following general formulation wherein thevalues are on a dry basis weight:

Parts dry Polyvinyl alcohol to Cypel resin 0.3 to 10 Pigment (kaolinclay) 18 to 60 Mela-mine formaldehyde 0.2 to 5 Salts (aluminum chlorideand zinc acetate) 1.5 to 30 The total solids may range between %25% withthe viscosity ranging from 400 to 800 centipoises. If there is an excessof water strike-through of the web may occur and there may be difficultyin drying. If there is too little water the mixture will be too viscousand will not flow properly in the equipment.

Certain procedural and formulation changes may be made in Step One ofthe foregoing example. The solu tion of aluminum chloride and zincacetate can be held out and added at the end of the make-down procedure.Similarly the Cypel Resin Emulsion may be held out and added after theheating or cooking step provided that it is added prior to the additionof the salt solution. Up to about 75% of the melamine formaldehyde maybe replaced with melamine provided a small amount up to about of themelamine formaldehyde is added after cooking but prior to the additionof the salts.

The following examples represent preferred functional coatingformulations:

Example 2 Parts dry PVA 10 Cypel (63% ethylacrylate, acrylonitrile, 2%methacrylic acid) Pigment (kaolin clay) Melamine formaldehyde 3 Aluminumchloride 5 line acetate 5 Water to give 20% solids.

4 Example 5 Parts dry PVA 5 Parez 0.2 Cypel 1 Salts 3 Pigment 18 Example6 PVA 10 Parez 5 Cypel 2 Salts 30 Pigment 60 Example 7 PVA 5 Parez l5Cypel 0 3 Salts 15 Pigment 40 Example 8 PVA 10 Parez 3 Cypel l0 Salts 3OPigment 46 Example 9 PVA 5 Paraez 1.5 Cypel 1 Salts 1.5 Pigment 22Example 10 PVA 1O Parez 3 Cypel 10 Salts 30 Pigment 6 Example 11 PVA 5Parez 0.2 Cypel 15 Salts 13 Pigment 18 Example 12 PVA 10 Parez 5 Cypel 2Salts 3O Pigment 60 The following are additional preferred examples ofthe formulation for Step 1.

The formulation of this Example 14 is prepared generally as describedfor Step 1 of Example 1 with these changes-(1) the melamine resinsolution is added where the Parez resin solution is added; (2) the saltsolution is withheld and not added until after cooling; and (3) themelamine formaldehyde resin solution is also added after cooling butprior to the salt addition.

In the foregoing formulations a preferred form of the polyvinyl alcohol(PVA) is one that contains approximately 3% polyvinyl acetate forviscosity control, this grade of polyvinyl alcohol being availablecommercially from Shawinigan Chemicals, Inc., under the proprietaryproduct named Gelvatol 391. The PVA functions in this system primarilyas a protective colloid which prevents coagulation of the Cypel Resin bythe salts and the melamine formaldehyde. While PVA may also act as afilmformer, it does not account for the hydrophillic properties of thefunctional coating. Thus, if the Cypel is omitted the plate does notremain hydrophillic but becomes, hydrophobic. Accordingly, PVA and Cypeldo not perform the same function in the single functional coating.

The PVA may be replaced in whole or part with hydroxyethylated starch,e.g., Penford Gum 280 or Pencoat, on a weight for-weight basis.

The Cypel Resin Emulsion No. 205 may be replaced With similarformulation wherein the ethyl acrylate content ranges from 55 to 85parts by weight, the acrylonitrile from 45 to 20 parts by weight and themethacrylic acid from 0.5 to 4 parts by weight.

Melamine formaldehyde resin is used to insolubilize the polyvinylalcohol or hydroxyethylated starch, thereby contributing to the barrierproperties of the coating and help control the imaging properties of theresulting coatings. This material is available commercially, one sourcebeing under the proprietary name Parez Resin from American CyanamidCompany or as Resloom M75 from Monsanto. The melamine formaldehyde maybe replaced with other cross-linking agents, such for example asdimethylol urea (DMU), glyoxal, or glutaraldehyde. In such replacementthese agents will be substituted in amounts stoichiometricallyequivalent to the melamine formaldehyde on the basis of the formaldehydecontent.

The formaldehyde resin may be largely replaced with melamine resinprovided sufficient formaldehyde resin is added prior to the solution ofsalts to impart the desired imaging characteristics to the plates.Recrystallized melamine commercially available from American CyanimidCompany may be used. This variation is illustrated in Example 14.

The zinc acetate and aluminum chloride salts act to modify the imagequality of the printing coat. These salts may be used in diiferentratios of one to the other, and in different proportions to the otheringredients to achieve various known imaging effects.

More specifically, the ratio of zinc acetate to aluminum chloride mayrange from about 1 part of zinc acetate to 1 part of aluminum chlorideto 4 parts of zinc acetate to 1 part of aluminum chloride. The aluminumchloride may be replaced with stoichiometric equivalents of ferricchloride and chromium chloride.

In the foregoing formulations the pigment provides the proper grain tothe printing surface which acts to retain the moisture in the non-imagedareas. The kaolin clay may be replaced in whole or part, by one or moreother inert mineral pigment materials such as blanc fixe, zinc oxide,titanium dioxide, or other fine pigments.

It will be appreciated that the back and functional coatings may beapplied on any of the various types of known coating equipment in usefor applying coatings to paper and other webs. The planographic printingplates provided in accordance with the foregoing examples may be used inknown manner as direct image masters and have the advantage of beingcapable of being imaged by other reproduction process of known type suchas that performed in one of the ufrently available Xerox copyingmachines.

What is claimed as new is:

1. A planographic printing plate comprising a paper base having applieddirectly onto at least one surface a dried and insolubilized coatinglayer thereon derived from a single coating application and providing aplanographic printing surface, said coating being formed from an aqueousdispersion of from about 5 to 10 parts by weight of a protective colloidselected from the group consisting of polyvinyl alcohol andhydroxyethylated starch; from about 0.3 to 10 parts by weight of amixture containing from about 55 to parts by weight ethyl acrylate, fromabout 45 to 20 parts by weight acrylonitrile and from about 0.5 to 4parts by Weight of methaccrylic acid; from about 18 to 60 parts byweight of inert mineral pigment; from about 0.2 to 5 parts by weight ofa resin material selected from the group comprising melamineformaldehyde resin alone and melamine resin plus melamine formaldehyderesin; and from about 1.5 to 30 parts by weight of a mixture containingfrom about 1 to 4 parts of zinc acetate and a salt selected from thegroup consisting of 1 part of aluminum chloride, about 1.2 part offerric chloride and about 1.2 part of chromium chloride.

2. A planographic printing plate comprising a paper base having applieddirectly onto at least one surface a dried and insolubilized coatinglayer thereon derived from a single coating application and providing aplanographic printing surface, said coating being formed from an aqueousdispersion containing from about 5 to 10 parts by weight of polyvinylalcohol, from about 0.3 to 10 parts by weight of a mixture containingapproximately 63% by weight ethyl acrylate, about 35% by weightacrylon'itrile and about 2% by weight methacrylic acid, from about 18 to60 parts by weight of inert mineral pigment, from about 0.2 to 5 partsby weight of melamine formaldehyde resin, and from about 1.5 to 30 partsby weight of a mixture containing 1 part of zinc acetate and from about1 to 4 parts of aluminum chloride.

3. The planographic printing plate of claim 2 wherein said inert mineralpigment is kaolin clay.

4. The planographic printing plate of claim 3 wherein said dried andinsolubilized coating is provided on one side of the paper base, and theopposite side is provided with a coating to prevent curl and impartdimensional stability.

5. A planographic printing plate comprising a paper base having applieddirectly onto at least one surface a dried and insolubilized coatinglayer thereon derived from a single coating application and providing aplanographic printing surface, said coating being formed from an aqueousdispersion containing about 10 parts by Weight of polyvinyl alcohol,about 2 parts by weight of a mixture containing approximately 63% byweight ethyl acrylate, 35 by weight acrylonitrile and about 2% by weightmethacrylic acid, about 45 parts by weight of inert mineral pigment,about 3 parts of melamine formaldehyde resin, about 5 parts by weight ofaluminum chloride and about 5 parts by weight of zinc acetate.

6. The planographic printing plate of claim 5 wherein said inert mineralpigment is kaolin clay.

7. The planographic printing plate of claim 5 wherein said dried andinsolubilized coating is provided on one side of the paper base and theopposite side is provided with a coating to prevent curl and impartdimensional stability.

8. The method of making a planographic printing plate which comprises:coating a paper base web with a single application of an aqueousdispersion having a solids content ranging between about 15 to 25% byweight and containing from about 5 to 10 parts by weight of a protectivecolloid selected from the group consisting of polyvinyl alcohol andhydroxyethylated starch; from about 0.3 to 10 parts by weight of amixture containing from about 55 to 85 parts by weight ethyl acrylate,from about 45 to 20 parts by weight acrylonitrile and from about 0.5 to4 parts by weight of methyacrylic acid; from about 18 to 60 parts byweight of inert mineral pigment; from about 0.2 to 5 parts by weight ofa resin material selected from the group comprising melamineformaldehyde resin alone and melamine resin plus melamine formaldehyderesin; and from about 1.5 to 30 parts by weight of a mixture containingfrom about 1 to 4 parts of zinc acetate and a salt selected from thegroup consisting of 1 part of aluminum chloride, about 1.2 part offerric chloride and about 1.2 part of chromium chloride; and, dryingsaid coating.

9. The method of claim 8 wherein said aqueous dispersion is coated anddried on one side of the paper base web and a second coating is appliedand dried on the opposite side to prevent curl and impart dimensionalstability.

10. The method of making a planographic printing plate which comprisescoating a paper base Web with a single application of an aqueousdispersion having a solids content ranging between about 15 to 25% byweight and containing from about 5 to parts by weight of. polyvinylalcohol, from about 0.3 to 10 parts by weight of mixture containingapproximately 63% by weight ethyl acrylate, about 35%" by weightacrylonitrile and about 2% by weight methacrylic acid, from about 18 to60 parts by weight of inert mineral pigment, from about 0.2 to 5 partsby weight of melamine formaldehyde resin, and from about 1.5 to 30 partsby weight of a mixture containing approximately 1 part of zinc acetateand from about 1 to 4 parts of aluminum chloride, and drying saidcoating.

11. The method of making a planographic printing plate which comprisescoating a paper base web with a single application of an aqueousdispersion having a solids content ranging between about to by weightand containing about 10 parts by weight of polyvinyl alby weight of amixture containing. approximately 63% by weight ethyl acrylate, by'weight acrylonitrile and about 2% by weight methacrylic; acid, aboutparts by weight of inert mineral pigment, about 3 parts by weight ofmelamine formaldehyde resin, about 5 parts by weight of aluminumchloride and about 5 parts by weight of zinc acetate, and drying saidcoating.

12. The method of claim 11 wherein said aqueous dispersion is coated anddried on one side of the paper base web and a second coating is appliedand dried on the opposite side to prevent curl and impart dimensionalstability.

13. A planographic printing plate comprising a paper base having applieddirectly onto at least one surface a dried and insolubilized coatinglayer thereon derived from a single coating application and providing apianographic printing surface, said coating being formed from an aqueousdispersion containing from about 5 to 10 parts by weight of polyvinylalcohol, from about 0.3 to 10 parts by weight of a mixture containingapproximately 63% by weight ethyl acrylate, about 35 by weight acrylonitrile and about 2% by weight methacrylic acid, from about 18 to parts byweight of inert mineral pigment, a suflicient quantity of a formaldehydedonor to insolubilize the polyvinyl alcohol, and a sufficient quantityof at least one polyvalent salt to impart predetermined imaging effects.

cohol, about 2 parts References Cited UNITED STATES PATENTS 2,635,5374/1953 Worthen 101-1492 2,889,299 6/1959 Ritson. 2,994,676 8/1961 Kucsanet al. 3,006,274 10/ 1961 Oransky et al 101-149.2 3,020,839 2/1962Richard 101-1492 ROBERT E. PULFREY, Primary Examiner.

J. A. BELL, Assistant Examiner.

1. A PLANOGRAPHIC PRINTING PLATE COMPRISING A PAPER BASE HAVING APPLIEDDIRECTLY ONTO AT LEAST ONE SURFACE A DRIED AND INSOLUBILIZED COATINGLAYER THEREON DERIVED FROM A SINGLE COATING APPLICATION AND PROVIDING APLANOGRAPHIC PRINTING SURFACE, SAID COATING BENG FORMED FROM AN AQUEOUSDISPERSION OF FROM ABOUT 5 TO 10 PARTS BY WEIGHT OF A PROTECTIVE COLLOIDSELECTED FROM THE GROUP CONSISTING OF POLYVINYL ALCOHOL ANDHYDROXYETHYLATED STARCH; FROM ABOUT 0.3 TO 10 PARTS BY WEIGHT OF AMIXTURE CONTAINING FROM ABOUT 55 TO 85 PARTS BY WEIGHT ETHYL ACRYLATE,FROM ABOUT 45 TO 20 PARTS BY WEIGHT ACRYLONITRILE AND FROM ABOUT 0.5 TO4 PARTS BY WEIGHT OF METHACCRYLIC ACID; FROM ABOUT 18 TO 60 PARTS BYWEIGHT OF INERT MINERAL PEGMENT; FROM ABOUT 0.2 TO 5 PARTS BY WEIGHT OFA RESIN MATERIAL SELECTED FROM THE GROUP COMPRISING MELAMINEFORMALDEHYDE RESIN ALONE AND MELAMINE RESIN PLUS MELAMINE FORMALDEHYDERESIN; AND FROM ABOUT 1.5 TO 30 PARTS BY WEIGHT OF A MIXTURE CONTAININGFROM ABOUT 1 TO 4 PARTS OF ZINC ACETATE AND A SALT SELECTED FROM THEGROUP CONSISTING OF 1 PART OF ALUMINUM CHLORIDE, ABOUT 1.2 PART OFFERRIC CHLORIDE AND ABOUT 1.2 PART OF CHROMIUM CHLORIDE.